Monkey patch original current_thread _active

Monkey patch the original current_thread to use the up-to-date _active
global variable. This solution is based on that documented at:
https://github.com/eventlet/eventlet/issues/592

Change-Id: I8e8a9ce5085b7915994317af5ea903cf8a39e809
Closes-Bug: #1863021
(cherry picked from commit 44e77ea9a9)

neutron_dynamic_routing/cmd/eventlet/__init__.py

@@ -14,3 +14,9 @@ import eventlet
 
 
 eventlet.monkey_patch()
+# Monkey patch the original current_thread to use the up-to-date _active
+# global variable. See https://bugs.launchpad.net/bugs/1863021 and
+# https://github.com/eventlet/eventlet/issues/592
+import __original_module_threading as orig_threading  # noqa
+import threading  # noqa
+orig_threading.current_thread.__globals__['_active'] = threading._active